(1) Field of the Invention
The invention relates to a light emitting diode (LED) dimmer circuit comprising a typically commercially available triode for alternating current (TRIAC) dimmer, a rectifier and filter circuit, an energy storage and rectifier circuit, a buck converter circuit, a light emitting diode circuit and a buck filter circuit (or voltage-drop filter circuit) for modulating the illumination-purpose light emitting diode circuit, and making up the shortfall of the alternating-current (AC) voltage phase, caused by the conductivity phase angle of the TRIAC dimmer, for the energy storage applying the energy storage and rectifier circuit, so that the light output of the light emitting diode can achieve the stable and flicker-free effect in the dimming requirement of the light emitting diode either the micro bright or full bright requirement.
(2) Description of the Prior Art
Currently, the commercially available light emitting diode dimmer circuit can accept the product of the commercially available TRIAC dimmer, and is the fundamental technology using a bleeder current circuit to keep the normal function of the TRIAC, so that the output AC voltage of the TRIAC is acquired, decoded, and converted into a dimming signal to change the switching frequency of the main working crystal, to fix the DC voltage of the light emitting diode circuit, to modulate the current flowing through the light emitting diode circuit, and thus to modulate the light output of the light emitting diode circuit. Thus, the dimming effect of the light emitting diode circuit can be achieved. The adopted TRIAC dimmer drive integrated circuits (TRIAC Dimmer Drive ICs) include LM3445 of Texas Instruments (TI) and Steval-ILL044V1 of STMicroelectronics. The products manufactured by the TRIAC dimmer drive ICs have the following drawbacks.
First, because differences are present between various brands of commercially available TRIAC dimmers, when the commercially available light emitting diode circuit product for the same modulation works in conjunction with different brands or different types of TRIAC dimmers for phase modulation, the decoder for decoding the AC voltage of the TRIAC has an decoding error and thus generates different modulation ranges. Thus, the stable flicker-free dimming effect for the light output of the light emitting diode circuit cannot be achieved.
Second, the bleeder current circuit is composed of active device(s) and passive device(s), wherein both the selection of the active devices and the error of the passive device(s) make the current of the bleeder current circuit fluctuate. Thus, the stable flicker-free dimming effect for the light output of the light emitting diode circuit cannot be achieved.